It has been a history of more than 50 years for the development of a technology for improving oil recovery rate through injection of carbon dioxide (CO2), which has been widely applied worldwide as an important technology for improving the oil recovery rate. Among the total number of global EOR projects, gas drive projects account for 54%, i.e. among the global EOR projects, nearly half of the global EOR projects are gas drive projects; among all the gas drive projects, the number of CO2 projects accounts for as much as nearly 77% alone; therefore, the technology for improving the oil recovery rate with CO2 drive accounts for 41.46% of the total global EOR projects, which has become one of the most important techniques for improving the oil recovery rate.
However, in the on-site application of a carbon dioxide drive technology, the carbon dioxide will be subject to viscous fingering and gravitational differentiation in a displacement process due to its relatively low viscosity and density. The viscous fingering makes the injected carbon dioxide channel through bypassing replaced crude oil and reduces sweep efficiency, and when there are cracks in a stratum, it will be more serious. Therefore, the critical part for improving the gas injection effect is to control the fluidity of the carbon dioxide to slow down gas channeling.
At present, the common technologies for controlling the fluidity of the carbon dioxide can be a water gas alternating injection technology and a foam flooding technology. For the problems such as poor injectability of low permeability oil reservoir water and foam fluid and instability of conventional carbon dioxide foam, provided is a method for fully utilizing the characteristic that supercritical carbon dioxide is a good solvent, adopting the gas-soluble surfactant, and injecting it into the stratum by means of taking carbon dioxide as a carrier to carry the gas-soluble surfactant to produce supercritical carbon dioxide foam in order to control the carbon dioxide fluidity.
the supercritical carbon dioxide foam fluidity control technology based on the gas-soluble surfactant is still in an early stage of research and development, and the key to successfully apply this technology is to develop a high-efficiency low-cost carbon dioxide gas-soluble surfactant, wherein the high efficiency refers to: such surfactant
first, has good solubility in the supercritical carbon dioxide, i.e., being capable of taking carbon dioxide as a carrier;
second, has good foaming ability, i.e., being capable of producing foam when meeting water and having good foaming volume and foam half-life; and
finally, has good post-bursting foam regenerating property, i.e., after the foam bursts in a stratum, when carbon dioxide floats upwards under the action of gravitational differentiation, the gas-soluble surfactant can foam again under the carrying of the upward floating carbon dioxide.
Therefore, it needs to establish a set of device and method for actually and precisely evaluating the foaming property of the gas-soluble surfactant.